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  Java Practices -> Include 'from', exclude 'to'
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<div class='page-title'>Include 'from', exclude 'to'</div>

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There is a convention in the JDK involving <tt>from..to</tt> ranges of values. The convention is that 
<tt>from</tt> is included, while <tt>to</tt> is excluded. 

<P>Some examples from the JDK :
<ul>
<li>String.<a href='http://java.sun.com/javase/6/docs/api/java/lang/String.html#substring(int,%20int)'>substring(from, to)</a>
<li>List.<a href='http://java.sun.com/javase/6/docs/api/java/util/List.html#subList(int,%20int)'>sublist(from, to)</a>
<li>Arrays.<a href='http://java.sun.com/javase/6/docs/api/java/util/Arrays.html#copyOfRange(T[],%20int,%20int)'>copyOfRange(T[], from, to)</a>
</ul>


<P><b>Date Ranges</b><br>
A related issue is specific to date values. 
It's common to have a date range specified using dates only (with no time portion), while the underlying data actually includes both a date and a time.
This can easily lead to off-by-one errors.

<P>For example, taking the following expression :
<PRE>2010-01-01 <= x <= 2010-01-31</PRE>

then the following is true :
<P><table border='1' cellspacing='0' cellpadding='1'>
 <tr><th>Date x</th><th>In Range?</th></tr>
 <tr><td>2010-01-01 00:00:00</td><td align='center'>Y</td></tr>
 <tr><td>2010-01-01 01:00:00</td><td align='center'>Y</td></tr>
 <tr><td>2010-01-30 00:00:00</td><td align='center'>Y</td></tr>
 <tr><td>2010-01-30 23:59:59</td><td align='center'>Y</td></tr>
 <tr><td>2010-01-31 00:00:00</td><td align='center'>Y (usually)</td></tr>
 <tr><td>2010-01-31 00:00:01</td><td align='center'>N</td></tr>
 <tr><td>2010-01-31 02:00:00</td><td align='center'>N</td></tr>
</table>

<P>(The caveat for <tt>2010-01-31 00:00:00</tt> is made since it will depend on the details of how the comparison is made by the class which models the date/time - usually, it will be within the range.)

<P>The above table shows that times after <tt>2010-01-31 00:00:00</tt> are <i>excluded</i> from the range. This is usually not desirable.
In this case, you need to alter the comparison slighty to 
<PRE>2010-01-01 <= x < (2010-01-31 + 1 day)</PRE>

<P>Again, this uses the <i>include-from, exclude-to</i> style mentioned above.
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